The present invention relates to a differential gearing for vehicles.
Differential gearings primarily have the object of distributing an input rotational speed or an input torque to two gearing output shafts connected with driving wheels and, in the process, render possible the rotational speed differences occurring when cornering between the wheel on the inside during the cornering and the wheel on the outside during the cornering. During the transmission of high driving powers, differential gearing may become very hot. The prestressing of the bearings by way of which the differential holder is disposed in the differential gear housing will then frequently change as a result of thermal expansions. A decrease of the bearing prestress in the differential gearing has a negative effect on the acoustic behavior; that is, the gear cutting noise becomes louder. In addition, there is the danger that the service life of the differential gearing is reduced when the bearing prestress is changed.
From German Patent Documents DE 199 46 383 A1 and DE 196 07 336 A1, various possibilities are known for generating or maintaining a prestressing of the bearings. A prestressing force can be generated, for example, hydraulically, by spiral springs, disk springs, etc.
It is an object of the invention to create a differential gearing where the prestressing of the bearings of the differential holder rotatably disposed in the housing of the differential gearing remains as optimal as possible also at different operating temperatures.
The invention is based on a differential gearing for vehicles which is known per se and which has a gearing input and two gearing output shafts which exit from the differential gearing housing on mutually opposite sides. In the differential gearing housing, a differential holder is arranged in the area between the gearing output shafts. The differential holder is rotatably disposed in the differential gearing housing by means of a ball bearing arrangement which has an axial bearing prestressing defined by the mounting.
A basic principle of the invention consists of providing at least one disk spring which generates the axial prestressing of the ball bearing arrangement. By means of the at least one disk spring, it is ensured that the axial prestressing of the bearings remains essentially constant in the case of temperature-caused thermal expansions of individual differential gearing housing components.
According to a further development of the invention, the differential gearing housing consists of an aluminum material. Aluminum housings have the advantage that, in comparison to other casting materials, they have a relatively low specific weight. However, the relatively high coefficient of thermal expansion of aluminum frequently presents problems, which may lead to a considerable decrease of the bearing prestress in the differential gearing when conventional bearing concepts are used. By the use of at least one disk spring, even relatively considerable thermal expansions of aluminum housings can be compensated and the bearing prestress can be kept almost constant even at high operating temperatures.
The ball bearing arrangement can be formed by ball bearings whose outer races are stationarily connected with the differential gearing housing and whose inner races are slid onto shaft sections of the differential holder. The at least one disk spring may be arranged between the differential gearing housing and one of the outer races of the ball bearings.
The ball bearings may be angular contact ball bearings. The angular ball bearings may have an X arrangement.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings for example.